Motor control system



March l, 1932.

F. C. BIGGERT, JR`

MOTOR`CONTROL SYSTEM Filed Nov. 19,' 195o 2 sheets-sheet 1- March l,1932.

F. c. BIGGERT, JR

' uoToR'coNTRoL SYSTEM 2 `sheets-Sheet 2 LFiled NOV. 19. 1930 lNvENToRy@ WH'NESSES ma@ QM Patented Mar'. l, 1932 UNITED STATES FLORENCE c.BIGGERT, JR., or GRAFTON, PENNSYLVANIA, .assIGNon 'ro UNITEDEN-- PATENTOFFICE GINEERING & FOUNDRY COMPANY, OF PITTSBURGH, PENNSYLVANIA, A.CORPORA- TION OF PENNSYLVANIA MOTOR CONTROL SYSTEM application medNovember 19, 1930. serial No. 496,668.

This invention relates `to driving gear for intermittently operabledevices such as flying which is simple and sturdy of constructiomdependable in operation, and while not necessarily so limited in itsuse, is particularly adapted for operating flying shears of the typeillustrated and described in a copending application, Serial No.402,382, filed October 25, 1929, by John A. Smitmans and the presentinventor.

A more particular object, however, is to provide a novel form ofelectric motor especially designed for use with apparatus of the abovenoted` character, and in combination therewith a simple dependablecontrol system adapted to automatically control the operation of themotor in such a way as to reduce to a minimum both the mechanical andelectrical shocks commonly encountered in suchY installations. l

These and various other objects, as Well'as various other novel featuresand advantages of the invention, will become more apparent when thefollowing detailed description is position, and in dotted lines in itsstationaryl position; l

Fig. 3 1s a schematic diagram of a drlve motor and control systemembodying the in,

vention; and

Fig. 4 a schematic view of a circuit inter- -rupting mechanism employedto control the operation of the reversing switch utilized for reversingthe current in the armature circuit of the blade motor. c y

Referring to Fig. 1 of the drawings, a particular form of flying shear,intended for cutting'strip into predetermined lengths as it issues froma rolling mill, is selected for illustrating the invention, andcomprises an anvil roll 10 which is rotatably mounted in bearingscarried by a stand 11. This roll is driven by a variable speed electricmowr 13, hereinafter. referred to as an anvil motor, which is connectedto the rollby means of a suitable reduction gearing 12, and is adaptedto drive it 'at peripheral speeds according with the linear speed of thestrip which as will be appreciated, usually varies with different sizesof stock. v

Forv cutting the strip, a blade 14 is employed being arranged to workagainst the anvil roll 10 and make cutting engagement with the strip asthel latter passes over the roll.

This blade is mounted in a holder 15 c which is secured to a shaft 16that is, in turn,

motor 17 is rotated in a clockwise direction,

as viewed in Fig. 2, suiciently to move the blade over the anvil rolland return it to its original stationary position as also indicated inFig. 2 by the dotted lines.

For determining the position of rest or the starting position oftheblade, the base of the blade holder 15,y or other suitable member onshaft 16, is provided with a snail cam 18, see Fig. 2, at the outer endof which 'there vis formed a shoulder `19. This shoulder is adapted toengage, in aV counterclockwise direction,`theouter end of a dog 20,which is pivotally mounted on a lever 21. The inner endl ofthis dog is atail'pie'ce 22 which engages the inner surface of a collar 23, thisbeing in turn xedly secured to stand 11 in concentric relation withshaft 16. i To provide for adjusting the dog 204 so as to stop the bladein different positions, lever 21 is equipped;V with a'manually voperablelatch 24 which 1s arranged to engage in one or another'of a series ofteeth 25 formed on the outer periphery of the collar 23. When the dog isproperly positioned, asshown in Fig. 2, the blade 1s held at rest ata'sucient distance from the sur-- face ofthe lanvil roll to ermit thestrip to passl freelylbetweenthe lade and roll.

will also be noted that when the blade holder is rotated in a clockwisedirection the dog 20 does not interfere with its movement but ridesfreely upon the snail cam 18 snapping over the outer end thereof at thecompletion of each revolution, placing it in a position to stop anycounter-clockwise movement of the blade beyond the point determined bythe relative positions of the dog 2O and shoulder 19.

In accordance with the customary practice adhered to in the past,standard types of electric motors have been employed to perform thefunctions required of blade motor 17, and the operation of such motorshas been controlled by rather complicated combinations of resistors,relays, contactorsand other control apparatus, all of which add to theeX- pense of such installations as well as increase the possibility ofoperating troubles.

In accordance with this invention a special form of motor is providedfor such use which is not only simpler of construction but pre` sents amuch simpler and less difiicult control problem and is susceptible ofoperation with considerably less operating troubles than the motorsheretofore employed.

As viewed in Fig. 3, motor 17 which is constructed in accordance withthe invention comprises chiefly a double pole stator 26 and a rotaryarmature 27 upon which a single coil 28 is mounted. The terminals ofthis coil are connected to a pair of collector rings 29`and 30. Bearingon these are a pair of brushes 31Y and 32, respectively, which in turnare connected to line contactors L1 and L2. The field for the motor isprovided by field windings 33 which are shown here as being connecteddirectly to the source of current supply although they may be otherwiseexcited.

In accordance with such anarrangement when direct current is supplied toboth the eld and armature windings the armature, instead of rotatingcontinuously, revolves only suiiciently to reach a position of magneticequilibrium. In doing so, however, it usually oscillates, due to theinertia of the moving parts, with a decreasing amplitude until theposition of ,equilibrium is reached. The amount of movement the armaturemakes in this manner, not considering that occa-- sioned by the inertiaof the moving parts when the current is reversed, is 180 electricaldegrees, which, in the case of a two-pole machine such as illustratedhere, is also 180 mechanical degrees or, in other words,'onehalf of acomplete revolution. This movement of thel armature is of courserepeated each time the currents in eitherthe armature or field wiiidings is reversed. To adapt such a motor to the driving of blade 14,armature 27 is coupled to shaft 16 by means of a 1 to 2 ratio gear unit,whereby the shaft is caused to rotate through4 a complete revolution foreach one-half revolutionl of the motor. The blade is thus caused to passover the anvil roll each time the current in the armature or fieldwindings is reversed.

For controlling the operation of motor 17 so that the shear may beoperatedintermittently as desired, the following equipment is employed.F or reversing the current to the armature a simple reversing switch 34is provided which, as illustrated in Fig. '3, comprises a pair ofbridging members 35 and 36 carried by a stem 43. Cooperating with thesebridge members are two different sets 37, 38 and 39 and 40,respectively, of contact elements which are connected in the powercircuit of line conductors L1 and L2. As il.- lustrated in the drawings,line conductor L1 is connected to the set of contact elements 37 and toone each of the contact elements 33 and 40, and line conductor L2 to theset of elements 39 and to one of each of the sets 38 and 40. Hence, whenthe bridging members 35 and 36 are actuated to their upper positionsbrush 31 is connected to line conductor L1 and brush 32 to lineconductor L2, and when to their lower positions the connections arereversed.

For holding the bridging members 35 and 36 in a neutral position betweenthe Contact elements when the switch is not in use, a pair of springs 41and 42 are attached to the opposite ends of the stem 43, and, foractuating switch 34, a pair of oppositely excited solenoid coils 44 and45 are employed and arranged in a circuit whereby their'energization iscontrolled by a manually operated switch 46 together with a pair of flagswitches 47 and 48, which latter are operated in accordance with themovements of the cutting blade. v

As illustrated in .Fig 4, the flag switches 47 and 48, each comprises apair of sliding Contact members (47a and 48a) which are connected incircuit relation, respectively, with the contact elements 46a and 46?)of switch 46 and the opposite ends of the coils 43 and 44 with `theirfree ends spaced from each other and arranged to ride upon the surfaceof a plurality of uniformly spaced commutator-like bridging members 4')mounted on a supporting disk 51 and insulated from one another. Foractuating disk 51 a double armed member 52 is secured to the endof ashaft 53 on which armature 27 is mounted, the disk 51 and switch members47a and 48a being associated therewith in the manner indicated in Fig. 1at the outer end of motor 17 adjacent to the collector rings 31 and Onthe end of each of the arms of the member 52 there is pivot'ally mountedat latch 54 which is held in place vby a spring 55 and prevented frommovement in one direction by a lug 56. Each time the motor is energizedto move the cutting bladeover the anvil roll these arms are' movedthrough la net angular distance of 180, and with each cut one of .thempasses its latch 54 over a portion of against the action of spring 55without moving disk 51 which isl mounted for movement in one directiononly. -When the direction. of motion of armature 27 is reversed after itover-travels the pointof magnetic equilibrium as referred to above, arm52 moves latch 54 back over the edge of disk 51 and in this backmovement engages one of the pins 58 andmoves disk 51. The pins 58,members 49 and the contact members 47 a and48a are so designed andspaced that each timeone of the arms of member52 moves in a counter- Iclockwise direction over disk 51 it moves disk to hereinbefore,wlien themotor 51 and the contact members49 sui'liciently to break the circuitthroughV one of the iag switches and close it through the other. Henceswitch 34 is caused to operate in a. different direction each time it isenergized, and isenergized by throwing switchv 46 in the direction ofwhich ever of the switches 47 or 48 is closed. Y

In accordance with the foregoing, when it is desired to make a cut,switch 46 is moved to one or the other of its circuit closing positionsdepending upon which one of the flag switches 47 or 48 is closed. Whenso closed reversing switch 34 is moved accordingly, causing the bridgingmembers 35 and 36 to. be moved into a corresponding circuit makingposition, and the armature coil 28 of the motor is thereby energized,With the energization' of coil 28, the armature 27 moves rom itsposition of rest determined by dog 2() carrying blade 14 over anvil roll10.'- Due to the inertia of the moving parts as referred 'is energizedarmature 27 and blade 14 are car ied beyond the point of magneticequilibrium of `the armature and to a point beyond the normal positionof rest determined by dog 20. To

. slacken the speed of the armature in its return movement after suchover-travel so that it will not move against the dog 20 with a shock, a4resistor 59 is inserted inthe armature circuit. For accomplishing this ainagnetivc type circuit interrupter lis employed,-

complishing this end could be used.

although any other suitable means for acshown in Fig.,3, the bridgingmember of this 'interrupter is connected in a circuit extendingin shuntrelation about resistor 59, whilek for effect-ing is operation anactuating coil across the 'terminals ofithe l nected through a 'two-Awaybridge (S05-on switch 34 to the supply lines, a resistor 600 beingconnected to the switch 34 in a manner to shunt 4coil 61a whentheswitchis energized.` Due to such an arrangement the iii .terrupter 60, whichis normally held closed,

is adapted to fall open as soon as the counter-electromotive force inthe armature circuit of the motor falls to zero, which occurs atapproximately the point of physical reversal of thev armature. Foradjusting the breaker so that it will open the shunt circuit atdifferent times, an adjustable resistor 62 may be connected in seriesvcircuit relation with coil 61, and the coil so designed that. with theinsertion of resistor 59 in the armature circuit, there will beinsuilicient voltage present across the armature to pro duce sufiicientpull in the coil to reclose the breaker. Hence, when once insertedkresistor 59 remains in the armature circuit until the motor is broughtto rest. Furtherv To vary the peripheral speed ofthe blade l so that atthe time of cutting itwill accordwith the speed of the strip, either thelever 21 may be adjusted to vary the accelerating stroke of thearmature, or al variable resistor 63 arranged in the motor iield circuitmay Eel adjusted to change the strength of the In order to explain theoperation of the invention, assume that the anvil roll is run-- ning ata speed corresponding to the .speed of the strip and thata piece ofstrip is passing over it. l Also, assume that the motor is adjustedtoattain the proper cutting speed. With 'these conditions prevailing, anddisk 51 in the position villustrated to produce a cut, ifyswitch 46 ismoved to the left, it will cause/'reversingswitch 34'to move tQ its upper position and close the armature circuit setting the armature inmotion.- Upon being energized the armature will accelerateV until theneutral magnetic Aposition of coil 28 is reached. During such movement,blade 14 `will move over the anvil roll and cut the strip. Also, dog 20will ride over'cam 18 and the Hag switch operating mechanism ^will movein synchronisin with vthe blade. Dur; ing the latter part of the forwardmovement der 19 placing it in aposition to stop the blade when itsmovement is reversed, also latch 54 after moving over one of the pins 58will be in a position ready to engage the pin as the member 52 isreversed. lVhen the of the armature, dog 2Qhwill snap over shoulpoint ofreversallof armature 28 i'sreached as stated above contacter 60 fallsopen, and shortly thereafter on the reverse movement -lti of thearmature the disk 5l is moved suiliciently by member 52 to open flagswitch 47 and close flag switch 48. Ihis opening of the switch occursshortly before the shoulder 19 reaches the stop dog Q0, so that themotor is dcenergized when the blade comes to rest. Switch I8 in closingplaces that switch in the proper condition for insuring the correctenergization of coil 28 on the next succeeding cutting operation.

Among its chief advantages the invention provides an exceedingly simpleform of motor, eliminates the use of ,a commutator which is usually aconsiderable source of trouble, and in addition employs only a verysimple and dependable combination of control equipment; the lite ofwhich is materially l enhanced by reason o' the iiact that in theoperation of the motor it is not necessary to interrupt any electricalcircuits when it is carrying a heavy current, as no circuits, inaccordance with this invention, are opened during a period of heavyload.

According to the provisions of the patent statutes, I have explained theprinciple and Inode of operation of my invention, and have illustratedand described what I no w consider to represent its best embodiment.I-Iowever, I desire to have it understood that, within the scope of theappended claims, the invention may be practiced otherwise than asspecifically illustrated and described.

I claim:

1. In combination with a work element, a direct current motor operablycoupled thereto comprising a stator and a wound rotor, slip ringsmounted on said rotor and connected to the terminals of the rotorwindings, a source of direct current connected to said slip rings, meansfor normally stopping the rotor at a position of rest displaced from itsposition of magnetic equilibrium, means for reversing the flow ofcurrent to the slip rings, automatic means for damping the oscillationsof the rotor each time it is moved by a reversal v of current, andmeansadapted to automatically interrupt the current supply to said slip ringsafter the rotor has moved a net total of 180 electrical degrees witheach reversal of current supplied to it.

2. In combination with a work element, a direct current motor operablycoupled thereto comprising a wound rotor, a pair of slip rings mountedon said rotor, a source of direct current supply connected to said sliprings, a reversing switch for reversing the flow of current to saidrings, and means Jfor automatically opening said switch after eachmove-l ment of the rotor corresponding to a movement of 180 electricaldegrees of said rotor winding, and means for insuring a reversal of thecurrent each time the reversing switch is actuated.

3. In combination with a Work element, a direct current motor operablycoupled thereto comprising a wound rotor, a pair of slip rings mountedon said rotor and connected to said rotoi` windings, a source .of directcurrent supply connected to said slip rings, means for reversing theflow of current to said rotor windings, automatic means for interruptingsaid current supply after each 18() degrees of electrical movement ofsaid rotor, and means for insuring unidirectional movementl of the rotorfor 'each reversal of current supplied to it.

Il. The combination with a rotary shear, of a direct current motor,comprising a wound rotor, means for positively coupling said rotor tothe shear in such a way that the shear' is rotated through a completerevolution each time the rotor is moved a distance corresponding to 180electrical degrees, a pair of slip rings mounted ou said rotor andconnected to the terminal of said rotor windings, a source of directcurrent supply connected to said slip rings, means for normally holdingthe shear in an inoperative position, means for interrupting the sourceof current supply to the slip rings after each rotation of the shear,means for insuring a reversal of current flow to the slip rings eachtime the motor is energized, and means operable at the will of anoperator for energizing the motor.

5. The combination with a. rotary shear, of a direct current motorcomprising a wound rotor, means positively coupling Asaid rotor to theshear in such a way that the shear is rotated through a completerevolution each time the rotor is actuated through an angular distanceof 180 electrical degrees, a pair of slip rings mounted on said rotorand connectedto said rotor windings, a source of direct current supplyconnected to said slip rings, and means for varying the cutting speed ofthe shear.

6. The combination with a rotary shear, of a double poled direct currentmotor comprising a wound rotor equipped with a single coil of magneticwindings, a pair of slip rings mounted on the rotor and connected tosaid windings, a source of direct current supply connected to said sliprings, means coupling said rotor to said shear in such a way that eachhalf revolution of said rotor produces a complete revolution of theshear, means for interrupting the dow of current to the slip rings aftereach complete rotation of the shear, means for reversing the iow ofcurrent to the motor for each successive operation of the shear, andmeans for stopping said shear in a selected inoperative position aftereach operation which is such as to insure movement of the rotor andshear in the same direction each time the current through the rotor isreversed.

In testimony whereof,.I sign my name.

FLORENCE C. BIGGERT, JR.

